1. Field of the Invention
The present invention relates to a printer suitable for use in a point-of-sale (POS) system, for example, and relates more particularly to a mechanism for opening and closing the print medium transportation path for loading the print medium to the printer.
2. Description of Related Art
Printers of this type generally have a printing mechanism for printing to a print medium in roll form, referred to simply as roll paper below. A typical printing mechanism has a print head and a platen. When roll paper is loaded into the printer, it is necessary to hold the paper unrolled from the paper roll by the printing mechanism or, more precisely to pinch it between the print head and the platen. For convenience, the platen is therefore usually disposed to the cover for covering a compartment for the roll paper while the print head is disposed on the printer frame so that the roll paper transportation path can be opened and closed. When the cover is then closed, the roll paper is pressed against the print head by the platen so that the printer prints on the roll paper held between the print head and platen.
Some printers of this type also have a paper cutting mechanism on the downstream of the printing mechanism along the paper transportation path in the paper transportation direction for cutting the printed roll paper for issuing a receipt, for example.
This paper cutting mechanism, or paper cutter, typically has a movable blade and a stationary blade on opposite sides of the paper transportation path. The stationary blade is typically on the cover and the movable blade is on the printer frame. When the cover is closed, the movable blade is positioned opposite the stationary blade with the paper transportation path therebetween so that the paper disposed between the movable blade and stationary blade can be cut by sliding the movable blade crosswise to the stationary blade. An exemplary printer of this type is taught, for example, in U.S. Pat. No. 5,579,043.
One of the drawbacks to a printer such as this is that because the platen of the printing mechanism is provided on an operable cover for opening and closing the paper transportation path, engagement of the platen and print head can vary when the cover is closed if there is any play in the support shaft on which the cover opens and closes. This can lead to a drop in print quality.
Another drawback to such printers having a paper cutting mechanism is that because the stationary blade of the cutting mechanism is provided on an operable cover for opening and closing the paper transportation path, engagement of the stationary blade and movable blade will not be consistent when the cover is closed if there is any play in the support shaft on which the cover opens and closes. This can lead to deficient cutting of the print medium.
Furthermore, the distance between the cover support shaft and the printing mechanism and paper cutting mechanism is great in a printer of this type in which roll paper of a large diameter can be used, and the same problems occur when the dimensional precision of the cover is poor or cover rigidity is low.
The present invention seeks to solve these problems with the related art by holding the platen and print head of the printing mechanism appropriately positioned to each other, and thereby provide a printer capable of maintaining high print quality, regardless of the positioning precision of the cover support shaft or the dimensional precision or rigidity of the cover.
Furthermore, by holding the stationary blade and movable blade of the paper cutting mechanism appropriately positioned to each other regardless of the characteristics of the cover, the present invention seeks to provide a printer that is free of the above paper cutting problems.
To achieve these objects, a printer according to the present invention has a cover (a first frame), a printing mechanism, a support member, and an alignment mechanism. The cover is disposed in a manner that it can be opened or closed with respect to a printer frame (a second frame), in which there is a transportation path for a recording medium, so that the recording medium transportation path can be opened or closed by moving the cover toward or away from the printer frame. The printing mechanism has a print head and platen disposed so that they can move to or away from each other with the recording medium transportation path therebetween. When these are moved to make the recording medium transportation path in mutually opposing positions, the printing mechanism can print to the recording medium passes between the platen and print head. The support member is movably mounted on the cover and supports either the print head or platen of the printing mechanism. When the cover is moved to the closed position to define the recording medium transportation path, the alignment mechanism is so configured as to align the one part, that is, the platen or the print head, mounted on the support member to the other part.
Even if the cover shifts slightly from the ideal opening and closing path due to variations in the positioning precision of a pivot of the cover on the printer frame, for example, the support member is aligned by the alignment mechanism to the predetermined position relative to the printer frame. In one embodiment of the present invention, the aligning mechanism comprises a guide mechanism and a holding mechanism. When the cover is moved to the closed position, the support member is guided to move to the predetermined relative position. Then, the support member is held in the position by the holding mechanism. To facilitate the above alignment operation, it is preferable to provide an elastic member between the cover and the support member. The elastic member positions the support member in a predetermined relative position range with respect to the cover thus configuring the guide mechanism when the support member first abut on the printer frame. It is further preferable to provide a stopper to regulate relative movement range of the support member to make engagement of the guide mechanism surer.
A printer according to the present invention further preferably comprises a pair of cutting blades disposed adjacent to the recording medium transportation path on the downstream side of the printing mechanism with the blades disposed movably to or away from each other with the recording medium transportation path located therebetween, and crosswise slideably to each other so that a print medium disposed therebetween can be cut when the blades are in a mutually opposing position. It is yet further beneficial that one of these blades is supported on the support member whereby the cutter blades are positioned to each other.
When the cover is closed to the printer frame according to one embodiment of the present invention, the support member is moved as described above to a position for aligning the printing mechanism. Because one of the blades is supported on the support member, thus positioning the support member also determines the mutual positions of the cutter blades.
Therefore, by thus positioning the cutter blades to a position at which they can slide crosswise relative to each other, a recording medium printed by the printing mechanism can be reliably cut by the cutter blades, and the cutting performance of the cutting blades can be maintained.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.